For many, Lean is the set of TPS 'tools' that assist in the identification and steady elimination of waste (muda), the improvement of quality, and production time and cost reduction. The Japanese terms from Toyota are quite strongly represented in "Lean". To solve the problem of waste, Lean Manufacturing has several 'tools' at its disposal. These include continuous process improvement (kaizen), the "5 Whys" and mistake-proofing (poka-yoke). In this way it can be seen as taking a very similar approach to other improvement methodologies.

There is a second approach to Lean Manufacturing, which is promoted by Toyota, in which the focus is upon improving the 'flow' or smoothness of work (thereby steadily eliminating mura, unevenness) through the system and not upon 'waste reduction' per se. Techniques to improve flow include production levelling, "pull" production (by means of kanban) and the Heijunka box. This is a fundamentally different approach to most improvement methodologies which may partially account for its lack of popularity.

The TPS has two pillar concepts: JIT (flow) and autonomation (smart automation). where they are therefore not at their most effective.
Lean implementation is therefore focused on getting the right things, to the right place, at the right time, in the right quantity to achieve perfect work flow while minimizing waste and being flexible and able to change. These concepts of flexibility and change are principally required to allow production leveling, using tools like SMED, but have their analogues in other processes such as R&D. The flexibility and ability to change are not open-ended, and therefore often not expensive capability requirements. More importantly, all of these concepts have to be understood, appreciated, and embraced by the actual employees who build the products and therefore own the processes that deliver the value. The cultural and managerial aspects of Lean are just as, and possibly more, important than the actual tools or methodologies of production itself. There are many examples of Lean tool implementation without sustained benefit and these are often blamed on weak understanding of Lean in the organization.

Lean aims to make the work simple enough to understand, to do and to manage. To achieve these three at once there is a belief held by some that Toyota's mentoring process (loosely called Senpai and Kohai relationship), so strongly supported in Japan, is one of the best ways to foster Lean Thinking up and down the organizational structure. This is the process undertaken by Toyota as it helps its suppliers to improve their own production. The closest equivalent to Toyota's mentoring process is the concept of Lean Sensei, which encourages companies, organizations, and teams to seek out outside, third-party "Sensei" that can provide unbiased advice and coaching, (see Womack et al, Lean Thinking, 1998).

Toyota develops Lean thinking

Toyota's development of ideas that later became Lean may have started at the turn of the 20th century with Sakichi Toyoda in their textile business with looms that stopped themselves when a thread broke, this became the seed of "Autonomation" and "Jidoka". Toyota's journey with JIT may have started back in 1934 when it moved from textiles to produce its first car. Kiichiro Toyoda, founder of Toyota Motor Corp., directed the engine casting work and discovered many problems in their manufacture. He decided he must stop the repairing of poor quality by intense study of each stage of the process. In 1936 Toyota won its first truck contract with the Japanese government his processes hit new problems and developed the "Kaizen" improvement teams.

Levels of demand in the Post War economy of Japan were low and the focus of mass production on lowest cost per item via economies of scale therefore had little application. Having visited and seen supermarkets in the US Taiichi Ohno recognised the scheduling of work should not be driven by sales or production targets but by actual sales. Given the financial situation during this period over-production was not an option and thus the notion of Pull (build to order rather than target driven Push) came to underpin production scheduling. It was with Taiichi Ohno at Toyota that these themes came together. He built on the already existing internal schools of thought and spread its breadth and use into what has now become the Toyota Production System (TPS). It is principally from the TPS, but now including many other sources, that Lean production is developing. Norman Bodek wrote the following in his foreword to a reprint of Ford's (1926) Today and Tomorrow: "I was first introduced to the concepts of just-in-time (JIT) and the Toyota production system in 1980. Subsequently I had the opportunity to witness its actual application at Toyota on one of our numerous Japanese study missions. There I met Mr. Taiichi Ohno, the system's creator. When bombarded with questions from our group on what inspired his thinking, he just laughed and said he learned it all from Henry Ford's book." It is the scale, rigour and continuous learning aspects of the TPS which have made it a core of Lean.